Residential water heaters, presently in use and being manufactured, comprise basically two types; i.e., the electric I.sup.2 R (resistance) type and the gas flame type. Both of these types are extremely inefficient in light of present concerns for energy shortages and conservation. While this invention also relates to newly manufactured domestic water heaters, one of the difficult problems solved by this invention is the conversion of the millions of both types of hot water tanks which are now in service.
The purpose of this invention is to achieve a manufacturing design and conversion design which will effect a Coefficient of Performance (C.O.P) in excess of the existing conventional apparati and methods. In experimentation, utilization of this invention has attained a C.O.P. of three or more over the electric (resistance) means of heating.
In the conventional hot water tank or either type, the cold water supply enters at the top and is conducted by the inlet conduit to a discharge point near the bottom of the tank. The main heat source is at or near the bottom of the tank and the cold water introduced is there heated. The heated water rises, through convection, and is withdrawn at the top of the tank.
In the conventional electric water heater there are two resistance heating elements. The main element is inserted through a threaded or bolted plate orifice near the bottom of the tank. The secondary or auxiliary element is inserted through a similar orifice near the top of the side of the tank. One form of this invention replaces the main element and leaves the secondary or auxiliary element undisturbed to function in its present capacity. Another form of this invention replaces one or both elements and accomplishes the heating of the water outside of the tank. This latter form is also especially useful in the conversion of gas flame heaters, because the only tank entry near the bottom is the drain port which provides available entry of only about 3/4" diameter. However, this latter form is also useful for the conversion of gas flame and electric water heaters by entry through the orifice provided in or near the top of the tank for the T & P valve by employing a long extension, terminating near the bottom of the tank, for offtake of the cold water.
In the conventional gas flame water heater, the main heat source is a gas burner mounted below the bottom of the tank and the secondary heat source is the centrally located flue through which the hot combustion gases ascend, imparting residual heat to the surrounding water and exiting at the top of the tank to be exhausted through the chimney flue. Since there is no need to exhaust combustion gases with the use of this invention, both heat sources may be replaced and the external connection to the chimney flue eliminated.
In both types of conventional water heaters lining material of considerable fragility, such as glass, is incorporated. Accordingly, in any conversion of heat source, it is important to utilize existing openings and avoid cutting new openings in the tank. However, this limitation does not pertain in the application of this invention to newly manufactured water heaters.
This invention relates to the apparati for replacing existing heat sources in existing and newly manufactured water heaters and the method for installing same in water heaters which are presently in use. The apparati basically comprises unique forms of the condenser tubing side of a standard refrigeration or air conditioning unit and the method is comprised in the manner in which the apparati are installed in replacement of or in substitution for the present conventional heat sources in water heaters. Since manufacturers of water heaters have large investments in design, tooling and production methods for the water heaters which are presently manufactured and marketed, this invention possesses utility in water heaters to be manufactured in the future, according to the present designs as well as those which are already in use, and also possesses utility in newly designed and manufactured water heaters, wherein more appropriate orifices may be provided to accomodate the entry and installation of the condenser tubing heating element.
In the present utilization of refrigeration and air conditioning units, the heat which is generated by the compressor and the condenser tubing is wastefully dissipated and its dissipation sometimes requires inconvenient of difficult installations. This invention provides a convenient, economic and useful means for the dissipation of that heat.
In all forms of this invention, the condenser tubing containing the hot refrigerant fluid, such as Freon, is in thermal conductive, but not intimate, contact with the water to be heated in the tank. The lack of intimate contact is intentionally maintained in order that the potable integrity of the water will not be violated by a potential failure of the condenser tubing and the resultant escape of refrigerant into the water in the tank. While it is not believed that all present regulations specifically require these safeguards, such will be promulgated, certainly. Accordingly, in the embodiments of this invention wherein the apparati are inserted directly into the water inside the heating tank and wherein the water is withdrawn from the tank and heated and reintroduced, the condenser tubing is surrounded by a sheath of corrosion resistant, thermal conductive material which is metallurgically compatible with the condenser tubing and which is outwardly disposed from and in uniform or intermittently variable spaced relation to the outside diameter of the condenser tubing. The inter-space or inter-spaces therebetween is filled with thermal conductive material, such as copper, aluminum, carbon, graphite, F.D.A. approved silicone, and the like, in powdered or finely particulate form or jelled or fluid state, or, alternatively, thermal conductive liquids, such as water, mineral oil and the like, or combinations of both types. However, in experimentation, it has been found that the use of water to fill the inter-space is effecient, safe, and convenient. External termini of the interspace are open or fragilely rupturable on the outside of the tank, in order that escape of the refrigerant be provided in the event of any failure of the condenser tubing, and to provide a telltale in the event of any failure of the sheath. The same type of sheathed tubing is utilized in this invention for the embodiment wherein the water is conducted outside of the tank, heated and reintroduced into the tank.
In the sheathed condenser tubing of this invention, it is desirable to maintain the inter-space relatively uniform between the outside of the condenser tubing and the inside of the sheath to insure reasonable uniformity in distribution of the thermally conductive material introduced therein while providing thermal conductive space preserving means to maintain optimum provision of heat transfer. For this purpose, a number of different embodiments of condenser tube and sheath design are incorporated in this invention. One such embodiment is comprised in spacer fins attached to the condenser tubing and extending radially outward therefrom to slidable contact with the inside of the sheath. Another such embodiment is comprised in reverse of the foregoing, with the fins attached to the inside of the sheath and extending radially inward therefrom to slidable engagement with the outside of the condenser tubing. Alternatively, advanced extrusion techniques permit the manufacture of the complete sheathed tubing with spacer fins fixedly engaging the inside of the sheath and the outside of the condenser tubing. Still another such embodiment is comprised in intermittently crimping the sheath bi-laterally into contact with the condenser tubing. Still another such embodiment is comprised in providing longitudinal or helical corrugations in either the condenser tubing or the sheath or both. It will be seen that other forms and combinations may be utilized, the important considerations being provisions of good thermal conductivity from the hot condensed refrigerant to the sheath and preservation of the potable integrity of the water.
The conventional operation of the standard refrigeration unit which is used in this invention comprises delivery of the refrigerant from the compressor to the condenser, passage though a drier and capillary expander, or other expansion device, vaporized passage through the cooling coils or evaporator, and back to the compressor. All of this operation is well known in the prior art and, excepting for the condenser, are not shown other than by general outline or discussed with particularity.
In the application of this invention to electric water heaters wherein entry of the condenser tubing and sheath is effected through the port which has accommodated the lower heating element, the form of a cylindrical helix or truncated conical helix is used. While the truncated conical form of helix permits the initially entering coils of the truncated end to be closer together, experimentation has disclosed that it does not result in placing any greater length of condenser tubing and sheath inside the tank than the cylindrical form of helix and is slightly more difficult to form. As explained hereinafter, it will be seen that the diameter of the helix, the distance between the coils, and the inside diameter of the water tank are all critically related considerations. The insertion of approximately eleven feet linear length of condenser tubing and sheath into the tank is adequate and has been accomplished through this invention. Of course, after the initially entered end of the helix contacts the opposite side of the tank, some compression or diminution of the space between the coils can be accomplished, thereby permitting the entry of some additional coiled tubing and sheath, but such compression of the helix is limited by reason of possible detrimental deformation and, perhaps, rupture of the condenser tubing or sheath or both. For consideration in fabrication of the cylindrical helix form, the entry limitation formula desirably requires that the dimension between adjacent coils be not less than one-half the outside diameter of the helix.
In older electric water heaters, the entry port for the resistance heating element is comprised in a bolt-on plate, while the newer models provide a threaded flange attached to the inside of the tank. In either case, the opening available for insertion of the helically coiled condenser tubing and sheath is in the nature of 11/4 inches in diameter. The entry is accomplished by inserting the leading end of the tubing and sheath into the tank port and causing rotation of the helix proximately around its longitudinal axis while keeping the helix in such position that the portion passing through the tank port is at the largest possible angle from the longitudinal axis of the port as is permitted by the dimensions of the cooperating elements. In this regard, it will be seen, as shown herein, that it is most advantageous that the major axis of a cross section of the condenser tubing and sheath be proximately perpendicular to the longitudinal axis of the helix. Desirably, for maximum insertion and minimum space between coils, the outer end of the major axis of the cross-section of the condenser tubing and sheath is canted toward the leading end of the helix. Obviously, in the embodiment of this invention wherein the water is withdrawn from the tank, heated and reintroduced, these critical dimension considerations do not exist.
In operation of the standard refrigerating unit utilized in this invention, the refrigerant is delivered from the compressor to the condenser at a range of approximately 140.degree.-180.degree. F., thereby providing an adequate heat source for heating the water to the customary temperature of 140.degree.-160.degree. F. Clearly, the refrigerant cools to a lesser temperature as it passes through the condenser, which is one of the purposes of the condenser in the refrigeration process. Since it is necessary, in this invention, that the refrigerant be carried by the sheathed condenser tubing both into and out of the tank, there must be a continuous inlet and outlet condenser tube and a continuous sheath, which sheath must be open or fragilely rupturable to the outside of the tank. It is not possible to make a sufficiently sharp return bend of 180.degree. at the leading or entry end of the helix without restrictively crimping the thin copper tubing used in the condenser tubing and the sheath. Therefore, this invention incorporates unique return caps for each, which are braised or soldered in place prior to insertion. It will be seen that the outlet condenser tube will be progressively cooler from the return point to exit from the tank and the inlet condenser tube will be progressively hotter from the return point to entry into the tank. While it is not necessary, it is possible to provide insulation between them when they are enclosed in a single sheath. Of course, in the embodiment wherein they are separately sheathed, there is no need that they be in attached contact. Heat transfer from the sheath to the water may be increased by the addition of thin radial thermal conductive fins attached in thermal conductive manner, such as soldering, to the sheath. While such fins cause some difficulty, and may be deformed, in the insertion procedure, such deformation is unimportant, since they continue to present additional heat transfer surface, even in deformed state. It is important, however, that such fins be provided on the sheath only at positions where they will be aligned proximately parallel with the convection flow of the water being heated. Otherwise, I have found that they will impede the convection flow, which is undesireable.
In the application of this invention to newly designed and manufactured water heaters, it is preferred to mount the compressor and evaporator of the refrigerating unit on top of the tank, as I have done also in some of the conversion applications of this invention. This arrangement conserves floor space and utilize space for the refrigerating apparatus which, ordinarily, is not used in the usual installation of a water heater. More important, however, I have found that the slight vibration which is imparted to the tank by the compressor greatly enhances the convection and resultant heating of the water. Also the heat imparted to the compresser from the warm tank prevents the accumulation of liquid refrigerant in the compressor and resultant slugging thereof. In such arrangement, for newly designed water heaters, the location and space limitation of an existing orifice for insertion of the sheathed condenser tubing into the tank is not pertinent, since an orifice which is appropriate in size and location is provided. In one such embodiment of this invention, the combined condenser inlet and outlet tubing enters through a provided orifice in the top of the water heater, along with the sheathing, and extends proximately to the bottom of the tank where it terminates in a helical coil or spiral. In another such embodiment of this invention, the combined condenser inlet and outlet tubing extends down the outside of the water heater, adequately insulated and encased, and enters through a provided orifice in the side of the tank proximate the bottom, along with the sheathing, and terminates in a helical coil or a multiplicity of bends.
A very efficient form of the invention in newly designed and manufactured water heaters is obtained by providing a vertical convection conduit or chimney positioned vertically in the tank and being approximately four (4) inches in diameter. This conduit may be attached to the top of the tank or the bolt plate through which the sheathed condenser tubing enters and exits, having its upper portion, in the nature of the top twelve (12) inches, pierced, and have its lowermost end disposed proximately above the bottom of the tank. Or, conversely, may be attached to the bottom of the tank, having its lower portion pierced, and have its uppermost end disposed proximately below the top of the tank. The sheathed condenser tubing is inserted inside this conduit and may be either the type which has a helical coil near its bottom extremity with a straight upward return therefrom, or the type which merely accomplishes four (4) or more vertical runs inside the conduit. The conduit is made of plastic tubing or other non-corrosive material, since its thermal conductivity is not important, and it is sufficiently large in diameter to permit a complete return bend of the sheathed condenser tubing without crimping, which requires about three (3) inches. In this embodiment of the invention, the convection commences with the cooler water near the bottom of the tank being heated by the sheathed condenser tubing inside and near the bottom of the conduit, rising much more rapidly than it would in the larger volume of the entire tank, exiting from the top of the conduit, and flowing downward as it cools or mixes with cooler water in the relatively much larger volume of that portion outside of the conduit. In addition, this design assures a concentrated flow of the hotest water to the upper portion of the tank, at the point of hot water take-off.
An adaptation of the immediately preceding described embodiment is also conveniently used in the conversion of existing gas flame water heaters. In this concept the outer flue, which is an extension of the concentric longitudinal internal flue, is removed because it is no longer needed. The lowermost end of the internal flue is plugged or capped, so that the flue is watertight and the gas burner beneath the bottom of the tank is removed and discarded. The sheathed condenser tubing, of one of the types hereinbefore described as being inside the convection conduit, is inserted downward into the internal flue, the flue is filled with thermal conductive material in powdered or particulate form, or with liquid such as water, and the top of the internal flue is left open or sealed with fragilely rupturable material. It will be seen, in this conversion concept that the sheath surrounding the condenser tubing could be eliminated and ordinary condenser tubing used, since the internal flue acts as a sheath. However, I do not recommend that as being safe and still prefer to use sheathed tubing for insertion into the flue, because many internal flues are badly corroded from combustion gases, and the internal flue may fail.